Functionalized construction of multiple active centers for durability controlling during catalytic combustion of chlorinated aromatic hydrocarbons

Abstract

The catalytic combustion of chlorine-containing VOCs primarily encounters the bottleneck of catalyst poisoning by chlorine, thereby impeding the further industrial application of this technology. The development of multi-active catalytic materials for discerning chlorine fixation, chlorine transfer, deep oxidation during elimination of chlorine-containing VOCs can mitigate catalyst chlorination and enhance stability. Herein, we utilizing LDHs as catalyst precursors and successfully synthesized flower-like Co2FexCr1-xOy catalyst with different functionalized reaction centers. The addition of Cr improved the surface lattice oxygen, oxygen vacancies, and acid sites of catalyst. The removal efficiency of CB can be achieved >90 % at 247 °C (WHSV = 33000 mL · g−1·h−1). The fixation of dissociated chlorine contributed by Cr not only enhances oxidation performance and directional adsorption of chlorine, but also improves carbon deposition resistance and catalyst sintering resistance significantly. Compared with Co2Fe1Oy, Co2Fe0.67Cr0.33Oy catalyst achieves a remarkable threefold reduction in surface carbon deposition. The DFT calculation revealed that water dissociation energy over the Co site is −0.72 eV, which is significantly lower than Fe (−0.59 eV) and Cr (−0.17 eV), facilitating water dissociation and subsequently removes a substantial amount of accumulated chlorine on Cr to form HCl. With the help of In situ DRIFT and GC/MS analysis, we found the efficient removal of chlorine atoms enhances the exposure of active sites on the catalyst surface with hydrolyzed hydroxyl group, which facilitating the conversion of aromatic hydrocarbons into a greater quantity of maleate and carboxylate species. This phenomenon is beneficial for the subsequent mineralization process of chlorobenzene. This work provide valuable insights for multi-active site catalysis mechanism in practical applications aimed at eliminating chlorinated organic waste gases from industrial emissions.